1. Field of the Invention
The present invention is related to an organic electroluminescent (hereafter “electroluminescent” is abbreviated as EL) display module and information terminal. Specifically, the present invention is related to a double-sided organic EL display module which is installed in an information terminal requiring a double-sided display, and an information terminal equipped with such double-sided organic EL display module.
2. Description of the Prior Art
With the spread of information terminals having an opening/closing portion such as portable telephones, notebook personal computers and the like, there has been a high demand to provide a display portion on both the front surface and the back surface of the opening/closing portion. On the other hand, spontaneous light emission type organic EL displays which are displays having high luminance at low power consumption are expected in display portions. In the prior art, in order to carry out display on both surfaces of the information terminal using organic EL display modules, two organic EL display modules need to be prepared for the front surface and the back surface.
FIG. 7 shows the structure of a prior art organic EL element display module for double-sided display. In FIG. 7, 30 represents EL light, 31 represents glass substrates, 32 represents transparent electrodes, 33 represents organic EL layers, and 34 represents metal electrodes. Because the metal electrodes 34 use a metal in which electron filling is easy at a low work function as a cathode, it is difficult to make the metal electrodes 34 transparent. On the other hand, in a metal electrode used as an anode, because a metal in which hole filling is easy at a high work function is applied, it is possible to use a transparent metal such as ITO (Indium Tin Oxide) or the like. For this reason, the EL light 30 emitted by the organic EL layer 33 at the intersecting points of the transparent electrode 32 and the metal electrode 34 is emitted from the glass substrate 31 side. Because it is difficult to emit EL light from the metal electrode 34 side, in order to carry out display on both surfaces of the information terminal, the structure uses two separate organic EL display modules in which the metal electrodes 34 form back faces as shown in FIG. 7.
In the prior art organic EL display module structure described above, two organic EL display modules are needed to carry out display on both surfaces of the information terminal.